Method for the production of a soldered joint

ABSTRACT

A method for the production of a soldered joint between at least two contact partners ( 22, 23 ) of a bonding arrangement ( 21 ), with a formed piece of solder material ( 27 ) being arranged at a distance to the bonding arrangement. The formed piece of solder material is at least partially melted off. The at least partially melted off formed piece of solder material being thrust against a bonding arrangement in such a way that both bonding partners are wetted in a bonding area to establish an electrically conductive bonding.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 37 CFR 1.53(b) of pending priorapplication Ser. No. 10/416,742 filed on Oct. 29, 2003, now U.S. Pat.No. 7,360,679 and claims the benefit of International ApplicationPCT/DE02/03365 of Sep. 10, 2002, which designated inter alia the UnitedStates and which claims the priority of German Application DE 101 45420.1 of Sep. 14, 2001.

FIELD OF THE INVENTION

The present invention relates to a method for the production of asoldered joint between at least two contact partners of a bondingarrangement where a formed piece of solder material is arranged at adistance to the bonding arrangement, the formed piece of solder materialis at least partially melted off and the at least partially melted offformed piece of solder material is thrust against the bondingarrangement in such a way that both contact partners are wetted toachieve an electrically conductive bond in a bonding area.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 5,828,031 discloses a method for the production of asoldered joint between two contact partners of a bonding arrangement,with the contact partners being designed as contact surfaces thatinclude a 90° angle. For the production of such a soldered joint, it isdescribed to arrange a formed piece of solder material formed as asolder ball by means of a capillary between the two contact partners insuch a way that the result is a contact between the two contact surfacesas well as the capillary. For this purpose, the solder ball is pressedagainst the contact surfaces by means of the capillary. Such contactmust be maintained long enough until a melting of the solder ball bymeans of laser energy has effected a wetting of the contact surfaces andthe resulting adhesive forces, which secure the solder material in thebonding position.

The aforementioned type of generation of the contact pressure betweenthe solder ball and the contact surfaces requires that the capillary forthe production of the soldered joint must be positioned directly in thearea of the bonding arrangement. For one, this requires an extremelyprecise positioning of the capillary, and on the other hand, it requiresa good accessibility of the bonding arrangement.

SUMMARY OF THE INVENTION

The invention is based on the problem of proposing a method for theproduction of a soldered joint between two contact partners of a bondingarrangement not arranged on the same plane, which requires on the onehand a low positioning effort for the positioning of the capillary, andon the other hand can be executed at a distance to the bondingarrangement, thus requiring lesser requirements with respect to theaccessibility of the bonding arrangement.

In the method for the production of a soldered joint in accordance withthe invention, a formed piece of solder material is arranged at adistance to the bonding arrangement and thrust or shot against thebonding arrangement following an at least partial melting off of theformed piece of solder material. This thrust motion or ballistic motionof the at least partially melted off formed piece of solder material issuch that both contact partners are wetted at the impact or as a resultof the impact on the contact partner(s). This can be effected in thatboth contact partners are impacted simultaneously or one contact partneris impacted first and the wetting of the second contact partner iseffected as a result of the ricochet effect. In any case, the wetting ofboth contact partners results in an electrically conductive joint.

Suitable solder materials are not only conventional materials such asmetallic solder alloys, for example, but principally all materials thatenable an electrically conductive joint between the contact partners,such as conductive plastic materials, for example.

Compared to the known method, this therefore results in a lesserrequirement with respect to the positioning precision of the capillaryon the one hand and with respect to the accessibility of the bondingarrangement on the other band, because a mechanical contact chainbetween the bonding arrangement, the formed piece of solder material andthe capillary for the production of the soldered joint is no longerrequired. Rather, the at least partially melted off formed piece ofsolder material can be positioned in the area of the bonding arrangementwithout contact to the capillary. Depending on the geometricalconditions or, for example, even the composition of the solder material,the formed piece of solder material may be thrust and/or shot againstthe bonding arrangement when only partially melted off or completelymelt off. It is essential only that both contact partners are wetted asa result of the impact of the solder material on at least one contactpartner of the bonding arrangement.

A particularly advantageous method is thrusting the at least partiallymelted off formed piece of solder material into a contact gap developedbetween the contact partners of the bonding arrangement. In suchapplication of the method, it is possible, depending on the developmentof the gap, to counteract the capillary force acting against the wettingof the entire contact surface of the bonding arrangement with the massforce of the solder material to achieve a dependable soldered joint evenwith bonding arrangements that are developed rather unfavorably.

Especially with a contact gap that is shaped more or less conically as aresult of the bonding arrangement, the application of the method enablesa dependable soldered joint if the at least partially melted off formedpiece of solder material is thrust into the direction of the bisector ofthe gap angle developed between the contact partners in the contact gap.The choice of thrust direction according to the bisector of the conicalgap is especially advantageous if the contact partners to be wetted aredeveloped as a surface with approximately equally sized contactsurfaces.

With a conical development of the contact cap and contact partners beingdesigned as differently sized contact surfaces, it is advantageous ifthe at least partially melted off formed piece of solder material isthrust into the contact gap along an axis that runs between the bisectorof the angle and the larger of the two contact surfaces.

With a bonding arrangement of two contact surfaces arranged in parallel,it is especially advantageous to thrust the at least partially meltedoff formed piece of solder material into the direction of the centeraxis of the gap into the parallel gap developed between the contactsurfaces of to the bonding arrangement.

In contact surfaces that are arranged relative to one another in thisway and/or contact gaps developed in this way, such as is the case, forexample, with a so-called flip-chip contacting of a semiconductorcomponent such as a chip, on a substrate, the method thus enables in afirst step a defined relative arrangement of the contacting substrateswith oppositely arranged connecting surfaces at a precisely adjustablesubstrate distance and in a second step with precise adherence to thedefined substrate distance, a contacting of the substrates by producinga soldered joint by means of a thrust application of the solder materialin the contact gap developed between the contact surfaces of thesubstrates.

With a bonding arrangement comprised of a contact sleeve and aconducting wire running in the contact sleeve, it is advantageous tothrust the at least partially melted off formed piece of solder materialinto the direction of the run of the conducting wire in theimplementation of the method. This application of the method appearsespecially advantageous when the substrate is assembled with electroniccomponents in SMD technology where the connecting conductors of thecomponents are assembled into the through plating of the substrate andsoldered with said through plating.

With a bonding arrangement comprised of a contact surface and a wireconductor arranged on the contact surface, the wire conductor is forcedinto contact with the contact surface as a result of the thrust of thesolder material on the wire conductor. In this way, it is also possibleto do without a contact between the contact tool and the wire conductorin a wire conductor connection while establishing the connection.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a principal representation of a step of the method in theimplementation of the method for producing a soldered joint between twocontact surfaces of a bonding arrangement forming a contact gap;

FIG. 2 is a principal representation of a step subsequent to the step ofFIG. 1 in the implementation of the method for producing a solderedjoint between two contact surfaces of a bonding arrangement forming acontact gap;

FIG. 3 is a principal representation of a step subsequent to the step ofFIG. 2 in the implementation of the method for producing a solderedjoint between two contact surfaces of a bonding arrangement forming acontact gap;

FIG. 4 is a principal representation of a step subsequent to the step ofFIG. 3 in the implementation of the method for producing a solderedjoint between two contact surfaces of a bonding arrangement forming acontact gap;

FIG. 5 is a principal representation of a step subsequent to the step ofFIG. 4 in the implementation of the method for producing a solderedjoint between two contact surfaces of a bonding arrangement forming acontact gap;

FIG. 6 is a principal representation of a step subsequent to the step ofFIG. 5 in the implementation of the method for producing a solderedjoint between two contact surfaces of a bonding arrangement forming acontact gap;

FIG. 7 is a view of a bonding arrangement forming a contact gap, withdifferently sized contact surfaces;

FIG. 8 is a side view of a particular arrangement using the method forproducing a soldered joint between contact surfaces of the bondingarrangement forming a parallel gap;

FIG. 9 is a top view of the arrangement shown in FIG. 8;

FIG. 10 is a view showing the application of the method for producing asoldered joint with a contact arrangement forming a ring gap; and

FIG. 11 is a view showing the application of the method for producing asoldered joint with a contact arrangement comprised of a contact surfaceand a wire conductor.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, FIGS. 1 to 6 show a soldermaterial application means 20 suitable for the implementation of themethod as well as the application of the method for producing a solderedjoint in a bonding arrangement 21 having contact partners that aredesigned as contact surfaces 22, 23 and arranged relative to one anothersuch that they form a conical gap 24. In the present case, the angle αof the conical gap 24 is approximately 90°.

FIG. 1 shows the solder material application means 20 having a guidechannel 26 developed in an application mouthpiece 25, which takes up toand guides the formed piece of solder material 27, which is designed ina ball-shape in the present case. The formed piece of solder material 27is moved by the gravity or the active load, for example by compressedgas, into a funnel-shaped output area 28 of the guide channel 26 whereit comes to bear on an opening edge 29 of the output area 28. In thepresent case, the opening edge 29 is developed like a valve seat andforms, together with the formed piece of solder material 27 arrangedopposite thereof, an essentially fluid-tight closing of the output area28. Because of the funnel-shaped design of the output area 28, anappropriate positioning of the application mouthpiece 25 above thebonding arrangement 21 enables a defined alignment of the formed pieceof solder material 27 on a plane that runs essentially perpendicular tothe longitudinal axis of the guide channel 26.

After the formed piece of solder material 27 has reached the guidechannel 26 of the application mouthpiece 25, as shown in FIG. 1, itcomes to bear on the opening edge 29 of the output area, as shown inFIG. 2.

Following the positioning of the formed piece of solder material 27relative to the bonding arrangement 21 shown in FIG. 3, the formed pieceof solder material is loaded with energy, for example by means of laserenergy, which effects an at least partial melting off of the formedpiece of solder material 27.

A temporary or even constant fluid pressure in the guide channel 26following the at least partial melting off of the formed piece of soldermaterial 27, which is preferably generated by means of a protective gas,effects the ejection of the at least partially melted off formed pieceof solder material 27 from the output area 28.

As shown in FIG. 5, the ejection process then effects a projectilemovement of the at least partially melted off formed piece of soldermaterial 27 into the direction of the bonding arrangement 21 along thecenter axis 31 of the guide channel 26, with the center axis 31approximately coinciding with the bisector of the gap angle α in theexample shown here.

As shown in FIG. 6, the impact of the formed piece of solder material27, which in the shown example was already completely melted off beforethe impact, results in a complete wetting of the contact surfaces 22,23. The development of the wetting is enhanced by the kinetic energy ofthe impact.

In the case that the formed piece of solder material 27 impacts thecontact surfaces 22, 23 of the bonding arrangement 21 in only partiallymelted off condition, there is first an at least partial wetting of thecontact surfaces 22, 23 corresponding to the portion of the melted offvolume of the formed piece of solder material 27. In that case, acomplete wetting of the contact surfaces 22, 23 can be ensured in thatthe formed piece of solder material 27 is repeatedly loaded with energyafter the formed piece of solder material 27 has impacted the bondingarrangement 21 until a complete melt off has been achieved.

FIG. 7 shows how the method can be adapted to the specific geometricalconditions of a bonding arrangement 32, which has differently sizedcontact surfaces 33, 34, depending on the orientation of the center axis31, which in the present case coincides with the ejection axis. To thatend, the ejection axis is tilted in deviation from the bisector 35 of anangle of a conical gap 36 formed by the bonding arrangement 32 towardthe larger contact surface 34 so that the impact of the at leastpartially melted off formed piece of solder material 27 results, in viewof the wetting surface, in a different wetting that is appropriatelyadapted to the respective size of the contact surfaces 33, 34.

FIG. 8 shows the application of the method for the production of asoldered joint between contact surfaces 37, 38 of a bonding arrangement39 forming a parallel gap 40.

The application example shown in FIGS. 8 and 9 relates to the example ofthe bonding of a chip 41 with peripherally arranged contact areas 37 ona substrate 42 also having peripherally arranged contact surfaces 38. Inthe present case, the substrate 42 with the contact surfaces 38 facingthe chip 41 is on a base 65. The chip 41 is arranged above the substrate42 and at a defined distance “a” to said substrate, with the contactsurfaces 37 of the chip being in an overlap with the associated contactsurfaces 38 of the substrate. In said defined relative position relativeto the substrate 42, the chip 41 is held by a negative pressure plate 43that has suction openings 45 in its suction surface 44 and effects anadhesion of the chip 41 to the negative pressure plate 43 by means of avacuum applied to the connection opening 46 of the negative pressureplate 43.

To produce soldered joints between the contact surfaces 37, 38 of theindividual bonding arrangements 39, the substrate arrangement 47comprised of the chip 41 and the substrate 42 is defined in its relativepositioning as described earlier. Then, as is shown especially in FIG.9, the substrate arrangement 47 is enclosed by a solder materialapplication means 48 such that respective associated application areas49 are assigned to the individual bonding arrangements 39. Therespective structure of said application areas 49 corresponds to that ofthe solder material application means 20 shown in FIGS. 1 to 7. In thatway, the center axes 31 of the application areas 49 are alignedessentially parallel and axial to the contact surfaces 37, 38, i.e.,approximately coaxially to the gap center axis 62 of the bondingarrangements 39.

As already explained in detail above with reference to FIGS. 1 to 6, theat least partially melted off formed pieces of solder material 27 areejected from said position, so that, following an impact of the at leastpartially melted off formed piece of solder material 27, as shown inFIG. 8 (right), the bonding surfaces 37, 38 are wetted to develop asoldered joint 50, as shown in FIG. 8 (left).

FIG. 10 shows an application of the method for the production of asoldered joint with a bonding arrangement 51 comprised of a contactsleeve 52 and a wire conductor 53, which, together form a ring gap 63.The contact sleeve 52 may be a through-contacting, called “via” intechnical jargon, in a substrate 54, into which a connecting conductor,designed as a wire conductor 53, of an electronic component such as asemiconductor component 55, for example, is inserted. The bondingarrangement between the semiconductor component 55 and the substrate 54shown in FIG. 10 thus corresponds to the connections established inso-called SMD (surface mounted device) technology to generate componentgroups.

To produce a soldered joint 56, shown in FIG. 10 in dash-dot lines, inthe ring gap 63 between the contact sleeve 52 and the wire conductor 53,the solder material application means 20 is positioned with the centeraxis 31 of the guide channel 26 relative to the contact sleeve 52essentially such that the center axis 31 runs essentially coaxially to acenter axis 57 of the contact sleeve 52. In the present case, the centeraxis 57 essentially coincides with the course of the wire conductor 53in the contact sleeve 52.

FIG. 11 shows the production of a soldered joint 64, shown in dash-dotlines, with a bonding arrangement 58 comprised of a contact surface 59of a substrate 60 and a wire conductor 61. The bonding arrangement 58 isloaded with the at least partially melted off formed piece of soldermaterial 27 from a position of the solder material application means 20where the center axis 31 of the application mouthpiece 25, whichcoincides with the direction of ejection, intersects the wire conductorand is arranged transversely to the contact surface 59. This positioningof the application mouthpiece 25 results in an intermediate arrangementof the wire conductor 61 so that the wire conductor 61 is pressedagainst the contact surface 59 by the impact of the at least partiallymelted off formed piece of solder material and enables an essentiallygap-free contact between the wire conductor and the contact surface 59.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

1. A method for the production of a soldered joint, the methodcomprising the steps of: orienting contact partners of a bondingarrangement relative to each other in a position with a location forreceiving material to form the solder joint; disposing a formed piece ofsolder material in an application device with a guide channelterminating at a mouth; arranging the mouth at a distance from thelocation for receiving material; at least partially melting the soldermaterial; ejecting the at least partially piece of melted soldermaterial from the mouth directed toward the location for receivingmaterial with the mouth at said distance from the location for receivingmaterial so the partially melted solder material strikes the locationfor receiving material resulting in wetting said contact partners withthe solder material for forming an electrically conductive connectionbetween said contact partners wherein said step of orienting includespositioning said contact partners to be oriented horizontally andsubstantially parallel to each other separated by a gap, and said stepof ejecting including thrusting solder into said gap along a pathsubstantially parallel to a plane of upper and lower contact partnersurfaces of said gap, said upper and lower contact partner surfacesbeing arranged on different substrates.